How to get translucency in parts of skin material?
To achieve the effect you are going for, there are 2 ways to do this, depending on what rendering engine you are using.  I will show you both ways to do it.
Using cycles:
to get translucency in certain parts of your mesh,  all you simply need to do, is turn up your subsurface value in the shader editor.  (see picture below)

after this, the light will shine through only in parts the mesh that are thin enough.  to adjust how much light you want shining through based on how thick/thin your mesh is, you can edit the &quot;subsurface radius&quot; values directly underneath the &quot;subsurface&quot; value on the &quot;principled BSDF&quot; node. (see image below)

After that, it's pretty much done.  You can adjust the other settings to your liking.
Using Eevee:
When using EV to achieve this result.  you do pretty much all the same things that you would do as if you were using cycles (read the above text first if you haven't already) except for one thing.  Make sure you have the desired object selected, then go to the materials tab, and enable: &quot;subsurface translucency&quot;.  (see image below)

Once this is done, it should work.  adjust other settings as needed.
And there you have it.  I hope this helped!  :)